As raw materials for cosmetics, paint, coating materials and lapping slurry for semiconductor wafers, high-purity raw materials with a minimal concentration of impurities, such as inorganic particles synthesized by a vapor phase method, such as fumigation, (hereinafter referred to as "vapor phased inorganic particles") have been used. However, the vapor phased inorganic particles are so intensive in secondary coagulation that when the vapor phased inorganic particles are dispersed in the water, it is necessary to destroy and fuse coagula of such vapor phased inorganic particles in the water. If the coagula are not completely destroyed or fused and consequently there remain many coarse particles, problems, such as increase in viscosity of the aqueous dispersion slurry as the time passes, gelation and consequent loss of fluidity, and sedimentation/separation of the coagula. As a result, the aqueous dispersion slurry of inorganic particles can no longer be applied to those uses as described above.
As a method of dispersing the vapor phased inorganic particles in an aqueous medium, a method using a dispersion equipment of high-speed mixing type (e.g., whirling blender, and high shearing mixer) as disclosed in U.S. Pat. No. 5,116,535 (Japanese Unexamined Patent Publication No. 3-50112) has been known. Also, a method using equipment combining a powder introduction type mixer/disperser (e.g., jet stream mixer) with a toothed colloid mill, a dissolver or a skim mixer (Nippon Aerosil Co., Ltd.; Catalog No. 19: How to Handle Aerosil, p. 38) has also been known. However, both of these methods are disadvantageous in that a long-time processing is required and that vapor phased inorganic particles cannot be completely destroyed or fused and consequently there remain many coarse particles and the above problem is resulted in.
Under these circumstances, the development of a method of producing the aqueous dispersion slurry of various inorganic particles has been wanted.